Evert,
Many thanks for the suggestion - it works! Below is a screen grab that shows the consequence of changing the QSL Sent Status from "I" to "N" for a verified LoTW QSO (I did this for RW0A as a test); it results in the Statistics and awards screen displaying correct information (after "settings->recalculate") for confirmed band/mode. I include the earlier screen grab with the incorrect indication for ease of reference (look at Asiatic Russia, 20m SSB)...

- log4om-capture-fixed.png (100.14 KiB) Viewed 3288 times
...and the original screen grab showing Asiatic Russia 20m SSB as unconfirmed, because the paper QSL sent status for all QSOs is set to "I" (I do this as I have a QSL policy of not sending any paper QSLs unless someone sends me a paper QSL first in which case I update the QSL status for the relevant QSO so as to generate a paper QSL for that QSO).

- log4om-capture.png (101.73 KiB) Viewed 3288 times
This is excellent news - many thanks Evert (and to Terry) for spotting this. Just for information, the entry in the Log4OM manual for the "I" status indicates the following:
I-Ignore or invalid – The user does not want to send a QSL, perhaps because it is a local station he works everyday, perhaps the QSO was with a pirate or unrecognized DXCC entity or a card checker rejected the QSO. (page 114)
This behaviour appears to be an unintended cascade consequence of selecting "I" for a QSO paper QSL status...